Research Pneumatic Servo Spot Welding Gun Control

Resistance spot welding is the main assembly connection technique for the assembly process of body-in-white. With the development of automobile industry in recent years, the market competition of automobile enterprises has become fiercer, so the requirement of increasing the welding quality and efficiency has become higher and higher. Because of the disadvantages like large impact of electrode to weldment, low precision in position control, poor efficiency and enormous electrode wear, the traditional pneumatic spot welding gun has been unable to meet the requirements of the automobile industry. In this case, the servo technologies of spot welding gun have got a rapid development. Among them, the pneumatic servo spot welding gun has attracted more and more motor corporations and pneumatic components manufacturers because of its high precision of electrode positioning, the flexible welding control, good integration with robot system and low cost compared to the electric servo gun. It will have broad application prospects.In this article, the servo technology of pneumatic servo spot welding gun is studied through theoretical analysis and experimental research, and the main work and achievements are as follows:(1) In order to study the control characteristics of pneumatic servo spot welding gun, the proportional valve control cylinder system for pneumatic servo gun has been studied by theoretical analysis and its mathematical model is established. The linear mathematical model is established through the working point linearization method. Based on this, the electrode cushion control and position control strategy is put forward and the simulation models of every stage for pneumatic servo spot welding process also are established by Simulink. The effectiveness of the control strategy is verified through the simulation analysis.(2) In order to further reveal the excellent properties of pneumatic servo spot welding gun, the influence of basic welding principle and main welding process parameters such as electrode stress is analyzed, and the pneumatic servo spot welding gun control technology experiment platform is set. By simulating the open-loop control mode of the traditional pneumatic welding torch, the different technical characteristics of the servo gun and traditional air gun in every stage of the welding process are analyzed. As a conclusion, the pneumatic servo spot welding gun has obvious technical advantage. It can help to make the control objectives clear in different welding stages for the experimental study. (3) Based on the analysis of control strategy, the real-time control procedures at each welding stage are written with RTW, and related experiments are completed. Firstly, different electrode target position control experiment in the process of gun open is conducted. High precision and strong robustness in electrode position control are realized. Secondly, the electrode cushion control experiment in the process of gun close is conducted. The high speed movement and small impact on weldment of electrode are realized. Thirdly, the electrode force control experiment is conducted. The experimental results indicate that the force control has rapid response and high precision. Meanwhile, variable electrode force control could be achieved.